Field of the Invention
This invention relates to a device for automatically setting a camera for the film sensitivity of a loaded film, and more particularly to an automatic film sensitivity setting device which is capable of automatically setting the sensitivity of a loaded film from electric signal terminals provided on the film case to indicate a specific film sensitivity in coded form.
Roll film packages recently released from Eastman Kodak of the United States bear on the circumference of the film case a bar code of a checkerboard-like pattern, which is generally called CAS (Camera Auto Sensing), consisting of a number of patches forming conductive metallic sections and insulating sections. These patches comprise film sensitivity data which indicate the sensitivity of the film by a binary code so that it can be read electrically.
There has already been proposed means for automatically reading the coded information or data of film sensitivity on the film case and introducing same to an exposure control circuit. According to this conventional means, upon loading of the film case with coded information of film sensitivity, the code is read by contacts provided in the film loading chamber of the camera and fed to a digital circuit where coded digital signals are converted to an analog signal by a D/A conversion circuit. This analog signal is fed to an arithmetic circuit to calculate and control the exposure on the basis of the film sensitivity and information of the subject luminosity received from a light measuring circuit.
In addition to the above-mentioned code reading contacts, the film loading chamber has to be provided with contacts exclusively used for detecting the film packages which have no coded information on the film cases. By the signals from these additional contacts, the operation is switched to the manual mode to supply the information of film sensitivity from a separately provided manual selector to the D/A conversion circuit, introducing the resulting analog signal to the arithmetic circuit.
According to this method, for the introduction of film sensitivity of film packages with the coded information, there have to be provided D/A conversion circuits in a number corresponding to that of the film sensitivity codes, resulting in a complicated circuit construction and an increased cost.
Further, it is necessary to provide separately a manual film sensitivity setting device along with encoder switches to permit manual setting for ordinary film packages without the coded information. This also gives rise to problems such as complicated construction and increased size.